As one type of conventionally-known gas treating device, there is an air purifying device for removing airborne dust, odors, and other matter by discharge. One such gas treating device is disclosed in JP, 2001-218828, A. This air purifying device is provided with a dust collecting filter and a plasma generating device. The plasma generating device has a plasma generating electrode plate and a counter electrode plate. And, by application of discharge voltage to both the electrode plates the streamer discharge takes place, wherein a plasma is generated.
In the above-described air purifying device, the dust collecting filter entraps and collects dust in the air. In addition, in the plasma generating device, unpleasant odorous components in the air are decomposed and removed by a substance of high reactivity (such as an activated species) contained in the plasma generated by the streamer discharge. And, the clean air, after removal of such dust and unpleasant odorous components, is released to outside the air purifying device as a stream of supply air.